Soaps have long been used for the washing of fabrics. More recently, soaps have been used far less frequently as the principle detergent active ingredient in modern fabric washing products. This is because difficulties have been experienced in dispersing and dissolving such products containing soap as the principle active ingredient, when employed in the washing of fabrics particularly at low wash temperatures. Furthermore, when such products have been employed in the washing of fabrics in hard water, in poorly built conditions, poor cleaning of the fabrics has resulted. This is because soil washed from the fabrics in such hard water conditions and suspended or dispersed in the wash liquor, can readily be redeposited onto the fabric, thereby interfering with the cleaning of the washed fabrics.
Cellulose ethers have previously been employed as anti-redeposition agents in detergent compositions containing nonionic and/or anionic non-soap detergent actives, but not where soap is a principle component of that composition.
It will be appreciated that in addition to its detersive activity, soap can also function as a builder by reducing the calcium ion concentration of hard water. This attribute can be of particular value in those territories or regions of the world where environmental pressures are forcing manufacturers to reduce the amount of the more conventional phosphate builders that they employ in detergent products. Hence, the present invention is particularly applicable to the formulation of low or zero phosphate products for use at low wash temperatures.
It has been proposed in British patent No. 1 534 641 (Unilever) to employ in the washing of fabrics, a powdered composition comprising from 5 to 15% by weight of an ethoxylated alcohol nonionic surfactant, and up to 0.25% by weight of a cellulose ether soil release agent. Optionally, up to 3% by weight of a water-soluble soap can also be present in the formulation as an aid for reducing the bulk density of the spray-dried powder described in this reference. These powdered compositions also preferably contain a substantial amount of sodium tripolyphosphate as a builder, typically between 30 and 40%, the weight ratio of this phosphate to the nonionic surfactant being at least 3:1.
We have now discovered that problems inherent in the use of detergent compositions containing soap as a principle detergent active compound ingredient, can be resolved by incorporation in such compositions of a special nonionic detergent active compound and a cellulose ether, especially when conventional phosphate builders are present in only a small amount or are omitted altogether from the composition.